Heavy wall drill pipe and method of manufacture of heavy wall drill pipe

ABSTRACT

A substantially homogeneous heavy wall drill pipe and its method of manufacture are disclosed. A cylindrical ingot is placed in a multi-hammer forging press to form the ingot into a drill pipe bar having a central protector portion and upper and lower connector sections each of larger diameter than cylindrical body sections of the drill pipe. Thereafter, the bar is straightened and upper and lower end connectors are machined. Threaded end portions are machined on the connectors and a bore is drilled through the drill pipe bar.

This is a division of application Ser. No. 602,385 filed Apr. 20, 1984now U.S. Pat. No. 4,674,171 issued June 23, 1987.

TECHNICAL FIELD OF THE INVENTION

The field of this invention relates to heavy wall drill pipe and themethod of manufacture of heavy wall drill pipe.

BACKGROUND OF THE INVENTION

In oil and gas drilling operations, it is universally known that thedrill bit is mounted at the end of a drill string which extends from thebottom of the hole being drilled up to a drilling rig. Typically, thedrill string extends through a rotary table which includes the equipmentfor rotating the drill string and thereby rotating the drill bit at thebottom of the drill string in order to drill the hole.

Basically, there are three types of drill pipe components that can beused in a drill string. The most common type of drill pipe is known bythat name and basically comprises elongated tubular pieces having a"pin" or male thread at one end and a "box" or female thread at theother end. Such standard drill pipe is typically 31 feet long and has auniform wall thickness in a range of 0.25-0.50 inches. Another type ofdrill pipe is known as the "drill collar". Drill collars are muchheavier than drill pipe and are typically located near the bottom of thehole. Drill collars are typically attached between the bottom of thestandard drill pipe part of the drill string and the drill bit itself.Drill collars typically have a greater wall thickness than standarddrill pipe and generally operate in a manner to provide weight thebottom of the drill string to urge the drill bit downwardly.

The third form of drill pipe is known as "heavy wall drill pipe".Typically, heavy wall drill pipe is approximately 31 feet in length andincludes upset end portions forming pin and box threaded connections andfurther has a central protector of larger diameter than the centralelongated body section. U.S. Pat. Nos. 3,784,238 and 3,773,359 discloseheavy wall drill pipe or intermediate drill stem having an elongatedtubular steel body terminating at either end in connectors of largerdiameter and further having an intermediate protector of larger diamterlocated intermediately between the ends of the elongated tubular steelbody. Typically, such intermediate drill stem is approximately 31 feetin length and has in its central section of uniform diameter a thicknessof at least 5/8 inch. Central protectors or sections of raised or largerdiameter are not wholly unique to heavy wall drill pipe. U.s. Pat. Nos.3,484,122 and 3,458,922 disclose standard drill pipe having centralprotector sections.

Typically, heavy wall drill pipe is manufactured from worn our drillcollars by machining the drill collar down in its central section to asection of small diameter leaving a central protector and upsets on theends. Heavy wall drill pipe can also be manufactured using tubing whichcan also be turned down on the ends leaving a central protector. Theupset ends for the connectors are then welded on U.S. Pat. Nos.3,784,238 and 3,773,359 disclose methods of manufacture of heavy walldrill pipe or intermediate drill stem. Manufacture of heavy wall drillpipe from a single piece of tubing by machining is quite undesirablefrom an economic standpoint due to the tremendous waste of material andmachine time. Therefore, most heavy wall drill pipe has beenmanufactured from tubes or pipes with connector portions being added toeach end. The utilization of welded on connector portions has generallybeen satisfactory; however, it is believed that it would be moredesirable from an economical and practical standpoint to manufactureheavy wall drill pipe from an integrally formed bar.

SUMMARY OF THE INVENTION

It is an object of this invention to manufacture drill pipe in anintegral form from a fully forged drill pipe bar. In summary, the methodof manufacture of an integrally forged drill pipe of this inventionincludes the steps of placing a substantially cylindrical ingot in amulti-hammer forging press and manipulating the ingot through the pressto form a substantially elongated fully forged drill pipe bar having anoutside surface formed of an indeterminate number of indentations causedby the impact of the forging hammers thereon. The drill pipe barcomprises a central body section having upper and lower generallycylindrical body sections and a centrally located protector section oflarger diameter and upper and lower end connector sections of largerdiameter. The drill pipe bar is then straightened such that thelongitudinal axis of the bar is a substantially straight line. The upperand lower end connectors of the drill pipe bar are then machined to formsubstantially cylindrical outside surfaces of the same outer diameter ateach end of the bar. The central protector is then machined to form agenerally cylindrical outside surface thereon. A bore is then machinedthrough the bar and an interiorly threaded end portion is machined inthe upper end connector and an exteriorly threaded end portion ismachined on the lower end connector.

The forged drill pipe of this invention comprises a generallycylindrical tubular body formed of a forged steel, the body having abore therethrough. The generally tubular body includes a central bodyportion having upper and lower body sections of substantially uniformoutside diameter. A central body section includes a central protectorintegrally forged with the upper and lower body sections. The centralprotector has a portion of a larger outside diameter than thesubstantially uniform outside diameter of the upper and lower bodysections. An upper connector section is integrally forged with the upperbody section. The upper connector section has a larger outside diameterthan the outside diameter of the upper body section and has aninteriorly threaded end portion in the body bore. A lower connectorsection is integrally forged with the lower body section. The lowerconnector section has a portion of larger outside diameter than thesubstantially uniform diameter of the lower body section and has athreaded end portion exterior to the body bore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the heavy wall drill pipe of the preferredembodiment of this invention illustrating the virtually entirely forgedoutside surface of the pipe;

FIG. 1A is a sectional view taken through the heavy wall drill pipealong line 1A--1A of FIG. 1;

FIG. 2 is a top view in schematic of the four-way forging machineutilized to manufacture the heavy wall drill pipe bar of this invention;

FIG. 2A is a side view in schematic illustrating the multi-impactforging action of the four-way forging press utilized to manufacture theheavy wall drill pipe of this invention;

FIG. 3 is a photograph illustrating the microstructure of the fullyforged heavy wall drill pipe bar;

FIG. 4 is a side view in schematic illustrating the boring of thecentral bore in the heavy wall drill pipe bar; and

FIG. 5 is a side view in section illustrating the pin and box endconnections on the end connectors of the heavy wall drill pipe andfurther illustrating the grooves machined in the end connectors for hardbanding.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, the letter H designates the heavy wall drillpipe of the preferred embodiment of this invention. The heavy wall drillpipe H is manufactured according to the process illustrated in FIGS.2-5. Basically, the heavy wall drill pipe H is formed of a generallytubular body generally designated as 10 of a forged steel. The generallytubular body 10 has a bore 10a there through. The body 10 includes acentral body section generally designated as 11, which body sectionincludes an upper central body section 11a and a lower central bodysection 11b. The central body sections 11a and 11b are of substantiallyuniform diameter.

The central body section 11 further includes a central protector 11cintegrally formed with the upper and lower body sections. The centralprotector 11c includes a cylindrical portion 11d of a diameter d-2greater than the diameter d-1 of the upper and lower body sections 11aand 11b, respectively.

The central protector cylindrical portion 11a is joined to the upperbody section 11a by an upper tapered portion 11e which tapers from thediameter d-2 of the protector cylindrical portion 11d to the diameterd-1 of the upper body section 11a. Similarly, a lower tapered portion11f extends from the cylindrical portion or surface 11d of the centralprotector and joins the diameter d-1 of the lower body section 11b.

The heavy wall drill pipe H further includes an upper connector sectiongenerally designated as 12 and a lower connector section generallydesignated as 14. The upper connector section 12 and the lower connectorsection 14 are both integrally formed with the upper and lower bodysections 11a and 11b, respectively, such that the heavy wall drill pipeH is a substantially homogeneous and integrally formed product.

The upper connector section 12 includes a cylindrical portion 12a havinga diameter d-3 larger than the diameter d-1 of the central body sections11a and 11b. The upper connector section 12 portion 12a is machined anda tapered portion 12b is machined and extends from the cylindricalportion 12a into and joins with the upper body section 11a. The upperconnector section 12 is known as the "box" end of the heavy wall drillpipe H and has an interiorly threaded section 12c (FIG. 5) adapted toreceive a screwed-in "pin" section of another heavy wall drill pipejoint or typical, thin walled drill pipe, drill collars, or other drillstem components.

The lower connector section 14 of the heavy wall drill pipe H includes amachined cylindrical portion 14a and a tapered portion 14b which is alsomachined. The cylindrical portion 14a has a diameter d-4 equal to thed-3 of the upper connector section 12 and thus greater than the diameterd-1 of the upper and lower sections of 11a and 11b, respectively. Thelower connector section 14 is the "pin" of the heavy wall drill pipe Hand therefore includes an exteriorly threaded portion 14c adapted to bescrewed into a box or upper connector section 12 of another piece ofheavy wall drill pipe, drill collar, or other drill stem component.

The upper connector cylindrical section 12a, the central protectorcylindrical section 11d and the lower connector cylindrical section 14aare all machined, cylindrical surfaces. A lower portion 12d of the upperconnector cylindrical surface 12a is hardbanded with a hard metal alloy.Part of the tapered surface 12b extending down to upper body section 11ais also hardbanded. Upper and lower portions 15a and 15b, respectively,of the central protector cylindrical section 11d are hard banded; and,an upper portion 14d of the lower connector section cylindrical portion14a is hard banded.

The remainder of the exterior surface of the heavy wall drill pipe Hother than the machined cylindrical and tapered portions 12a, 12b, 11d,14a and 14b and hardbanded portions or zones 12d, 15a and 15b and 14d isdimpled or indented in surface appearance. This dimpled appearance iscaused by the virtually indeterminate number of dimples or indentationsformed in the exterior surface of the heavy wall drill pipe as a resultof the forging technique utilized to manufacture the heavy wall drillpipe.

The length of the heavy wall drill pipe H is nominally 31 feet. Thelength of the upper connector 12 is at least 20 inches and the length ofthe lower connector is at least 27 inches. The length of the centralprotector section 11 is at least 18 inches. The thickness of the heavywall drill pipe in its upper and lower body sections having outerdiameter d-1 is at least 5/8 inch thick, which is of course, thickerthan the normal thickness of regular service drill pipe. The followingtable lists dimensions for some common connection sizes of the heavywall drill pipe H:

    ______________________________________                                                                Central                                               Nominal  End Connector  Protector                                                                              Tool Joint                                   Pipe Size                                                                              O.D.           O.D.     & Pipe I.D.                                  ______________________________________                                        31/2     43/4           43/4     2 3/16                                       4        51/4           51/4      2 11/16                                     41/2     61/4           61/4     27/8                                         5        61/2           61/2     31/8                                         ______________________________________                                    

Heavy wall drill pipe is manufactured in a manner to be describedhereinafter of a forgeable steel such as 4145H.

As previously described, to date heavy wall drill pipe has beenprincipally manufactured from worn drill collars or tubing. The mainbody section of such heavy wall drill pipe was machined from such worndrill collars or tubing and upper and lower connector sections wereadded by welding. If heavy wall drill pipe was manufactured from barstock, it was totally machined from such bar stock.

Heavy wall drill pipe H of the preferred embodiment of this invention ismanufactured by a forging process such that the heavy wall drill pipe His an integral piece of steel having no welds. The method of manufactureof heavy wall drill pipe H is illustrated in FIGS. 2-5.

Referring to FIGS. 2 and 2a, a four-way forging machine M isillustrated. The four-way forging machine M includes a central presssection 20 illustrated in FIGS. 2 and 2a. Of course, the illustrationsof FIGS. 2 and 2a are schematic of such a forging machine. Generallyspeaking, the forge press section of the forging machine M includes ahousing and mechanism for mounting four forging hammers 20a, 20b, 20cand 20d for rapid reciprocated and coordinated hammer movements againstan ingot I. The forging machine M further includes manipulating Sections21 and 22 which are mounted onto rail sections 23 and 24 located oneither side of the forge press 20 for the purpose of holding the ingot Iand moving the ingot relative to the forge press 20 and the hammers20a-20d.

Such forging machines M are known in the art. U.S. Pat. Nos. 443,030;3,098,402; 3,165,012; 3,224,244; 3,645,126 and 3,681,996 all disclosevarious aspects of such four-way forging machines. In each instance, thefour hammers or rams are located at 90° positions and various types ofdriving mechanisms, hydraulic or strictly mechanical, are provided forreciprocating the hammers radially with respect to the ingot I.Additionally, it is the state of the art to provide coordinated controlmeans to coordinate the movement of the manipulators 21 and 22 inconjunction with the rapid hammering of the forging hammers 20a-20d inorder to forge the ingot I to a desired configuration. It should beunderstood that other multiple hammer forging machines can also beutilized. In the preferred embodiment of this invention, the ingot I isa somewhat elongated cylindrical ingot having approximately a volume ofmaterial which would at least equal the volume of the solid, forgedheavy wall drill pipe. The ingot I is held by one of the manipulators 21or 22 at a time and the ingot I is moved longitudinally through theforging press 20 in a series of planned movements to forge out a heavywall drill pipe bar B such as illustrated in FIG. 2.

The heavy wall drill pipe bar B basically has the same configuration asthe finished heavy wall drill pipe product of H of FIG. 1. The heavywall drill pipe bar B is totally forged and solid. The bar B is asubstantially elongated tubular member having a first connector sectionof enlarged diameter 25a, a first intermediate body section of asmaller, uniform diameter 25b, a central protector section 25c of largerdiameter, a second central body section 25d of a smaller diameter and,finally, a second end protector section 25e of larger diameter. Theouter diameter of the connector sections 25a and 25e is somewhat largerthan the final diameter of the machined cylindrical portions 12a and14a, respectively. Comparing the bar B to the final heavy wall drillpipe H, the first central body section 25b of the bar exactlycorresponds to the upper body section 11a of the heavy wall drill pipeH. Similarly, the second body section 25d of the bar corresponds to thelower body section 11b of the heavy wall drill pipe H.

Referring to FIG. 3, a photograph is illustrated of the microstructureof the heavy wall drill pipe bar B. As the photograph illustrates, themicrostructure in the bar B is quite uniform and further, themicrostructure generally follows the contour of the outer surface of thebar B in its area of enlarged diameters such as the end portion 25ashown in FIG. 3. This uniform microstructure is a result of integrallyforging the bar B and heat treating the bar B as a whole. After theheavy wall drill pipe bar B has been fully forged in the forging machineM, the bar B is heat treated in its entirety in order to provide theuniform microstructure.

After the heavy wall drill pipe bar B has been heat treated, the bar Bis then straightened in a typical pipe straightening machine such thatthe longitudinal axis L (FIG. 4) of the bar B is virtually a straightline. Such pipe straightening steps are well known in the art and anytype of pipe straightening equipment may be utilized.

Before the bore 10 is drilled or machined through the heavy wall drillpipe bar B, cylindrical surfaces 12a, 11d and 14a are machined.Referring to FIG. 4, a boring machine known as a "treepanning" machineis illustrated schematically. In order to illustrate the operation ofthe treepanning machine T, the actual size of the heavy wall drill pipebar B is illustrated as being disproportionately large as to compared tothe treepanning machine T. The machined surfaces 12a, 11d and 14a areshown. In order to properly bore the bore hole 10a, it is necessary forthe cylindrical machined services 12a, 11d and 14a to be aligned alongthe axis. It is also necessary for the forged cylindrical surfaces 11aand 11b to be aligned along the same aforementioned axis. The diameterof the connector surface 12a, which is d-3, is equal to the diameter ofthe connector surface 14a, which is d-4. Thus the surfaces 12a and 14aare in the same cylindrical plane. The diameter d-2 for the centralprotector cylindrical portion 11d is equal to or less than the diametersd-3 and d-4 and therefore the cylindrical surface 11d is the samecylindrical plane or a plane concentric with the surfaces 12a and 14a.

Basically, the treepanning machine T may be any suitable variety ofmachine capable of boring the bore hole 10 through the heavy wall drillpipe bar B. One such machine is manufactured by LaBlonde Company.Typically, a treepanning machine such as T illustrated in FIG. 4includes a first support means 30 for engaging the cylindrical surface12a and a second support means 31 for engaging the cylindrical surface11d of the protector section of the bar B. A third support means orstation illustrated schematically as 32 supports the bar at the surface14a and further includes means for rotating the entire bar B. A boringdevice including a boring rod 33 having a boring bit 34 attached theretois mounted for rotation and longitudinal movement into the bar B alongthe longitudinal axis L of the bar. As the bar B is rotated, the boringrod 33 is advanced by a suitable mechanism into the bar and fluid iscirculated through the bar bore hole as it is created to remove thecuttings. In the treepanning machine T utilized, approximately one-halfof the bore 10 is machined in one side of the bar B, and, the bar B isthen removed and remounted in the opposite direction so that theremaining bore can be drilled or machined.

Referring to FIG. 5, the interior box thread 12c is machined into theupper connector 12 and the exterior, pin thread 14c is machined into thebottom end of the cylindrical surface 14a of the lower connector 14.

The heavy wall drill pipe bar is then hard banded. The box end 12 has agroove formed at 34a partly in the cylindrical section 12a and at 34bpartly in the tapered section 12b. Similarly, grooves (not shown) areformed in the upper and lower portions of the central protector in orderto provide the hard banding at 15a and 15b as illustrated in FIG. 1.And, a groove 35 is machined in the cylindrical surface 14a of the lowerconnector 14. Hard banding alloy is then welded into these grooves in amanner known to the art. In accordance with known hard bandingtechniques, hard banding material is added into the grooves such as 35using MIG welding techniques to weld into the groove, for example, acombination of a mild steel having tungsten carbide pellets therein tocreate the hard banded areas. Thereafter, the hard banded areas are heattreated in order to temper the area near the grooves which may have beensomewhat hardened as a result of the heat applied by welding.

The heavy wall drill pipe H is thus manufactured from a one piece forgedsteel bar, which steel bar is forged to the overall configuration of thefinal pipe product itself. Comparing the heavy wall drill pipe P toheavy wall drill pipe such as manufactured in accordance with U.S. Pat.No. 3,784,238, the heavy wall drill pipe H of the preferred embodimentof this invention has no welds and the only machined exterior surfacesare the cylindrical surfaces 12a, 11d and 14a and tapered surfaces 12band 14b. Other than these machined surfaces and the hard banding atzones 12d, 15a, and 15b and 14d, the entire remaining exterior surfaceof the heavy wall drill pipe P is indented or pocked as originallyforged. Therefore, the heavy wall drill pipe H is made with a minimum ofmachining on its exterior surface and additionally, has a veryconsistent microstructure as a result of being manufactured from anintegrally forged bar.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape and materials, as well as in the details of the illustratedconstruction may be made without departing from the spirit of theinvention.

We claim:
 1. A substantially homogeneous heavy wall drill pipe adaptedfor use in drilling operations such as oil and gas wells, comprising:agenerally tubular body formed of a forged steel, said body having a boretherethrough; said body including a central body section having upperand lower body sections of substantially uniform outside diameter; saidcentral body section including a central protector integrally forgedwith said upper and lower body sections, said central protector being aportion of said tubular body having an outside diameter larger than saidsubstantially uniform diameter of said upper and lower body sections; anupper connector section integrally forged with said upper body section,said upper connector section being of a larger outside diameter thansaid upper body section and having an interiorly threaded end portion insaid body bore; a lower connector section integrally forged with saidlower body section, said lower connector section being of a largeroutside diameter than said lower body section and having a threaded endportion exterior of said body bore, the outside surface of substantiallythe entire homogeneous heavy wall drill pipe being in its originallyforged condition; and said upper and lower body sections having agenerally cylindrical outside surface of substantially uniform outsidediameter formed of an indeterminate number of indentations produced byforging hammer impact.
 2. The structure set forth in claim 1, whereinsaid central protector includes:a generally cylindrical portion of alarger diameter than said substantially uniform diameter of said upperand lower body sections; and upper and lower tapered portions joiningsaid upper and lower body sections, respectively, to said generallycylindrical portion of said central protector.
 3. The structure setforth in claim 2, wherein:said generally cylindrical portion of saidcentral protector is machined and said upper and lower tapered portionshave indentations in their outisde surface that are formed by forginghammers.
 4. The structure set forth in claim 3, wherein:said upperconnector section includes a generally cylindrical outside sectionhaving a machined exterior surface and an upper connector taperedsection joining said generally cylindrical outside section of said upperconnector section and said upper body section; said upper connectortapered section having a machined outside surface.
 5. The structure setforth in claim 4, wherein:said lower connector section includes agenerally cylindrical outside section having a machined exterior surfaceand a lower connector tapered section joining said generally cylindricaloutside section and said lower body section; said lower connectortapered section having a machined outside surface.
 6. The structure setforth in claim 5, including:said generally cylindrical outside sectionof said upper and lower connectors each having an outside diameterlarger than said outside diameter of said generally cylindrical portionof said central protector and being in the same cylindrical plane witheach other.
 7. The structure set forth in claim 1, wherein:saidgenerally tubular body is formed of a high strength forgeable steel andsaid grain structure of said generally tubular body is substantiallyuniform and approximately follows the outside surface of said bodythrough said upper connector, upper body section, central protector,lower body section and lower connector.